Oxford Branch

British Cactus and Succulent Society

Cactus plants that require a compost containing limestone

Limestone a requirement or a poison ?

Many cacti and succulents grow exclusively in limestone areas, often within the cracks in the rocks themselves. Some, such as Aztecium and Geohintonia, take this to an extreme, apparently growing in a decomposing limestone or gypsum soil exclusively. What is not clear is whether they "require" this in order to flourish or are just better able to tolerate the conditions than other species, such that in their native habitat they survive where others perish. What does appear to be clear in greenhouse cultivation is that many cacti do not do well in acidic composts and do appear to benefit from some added limestone in the compost (limestone, NOT lime).

To this end, adding some granular limestone or limestone chips (3-5mm) to your compost and avoiding peat-based composts for some species, is generally accepted to be of benefit. Here is a listing (not claimed to be exhaustive) of species which should benefit from adding limestone to your compost.

It is also worth noting that if you do use a peat-based compost, adding limestone has been reported as causing a reaction which results in the mixture turning to a sludgy mess - not good for your plants - but I have no experience of this.

If you have any experience to add plants to this listing please let the web master know and we will update it.